#version 330 layout(std140) uniform State { int u_alphaTest; float u_alphaRef; // fog etc. }; uniform sampler2D tex; in vec4 v_color; in vec2 v_tex0; out vec4 color; void main(void) { color = v_color*texture2D(tex, vec2(v_tex0.x, v_tex0.y)); switch(u_alphaTest){ default: case 0: break; case 1: if(color.a < u_alphaRef) discard; break; case 2: if(color.a >= u_alphaRef) discard; break; } }